Optical unit and image display apparatus

ABSTRACT

The present invention discloses the structure of the array lens that at least any one of the diagonal size, vertical size and lateral size of lens cell is set to almost 1/(4.5 or more) for each corresponding size of the display elements, the structure that the diagonal size of lens cell is set to almost 0.18 inch or less, the structure that the total number of lens cells is set to almost 240 or more and the structure that the lens focal distance of lens cell is set to almost 30 mm or less.

This is a continuation of U.S. application Ser. No. 10/822,656, filedApr. 13, 2004, now U.S. Pat. No. 6,963,453, which is a continuationapplication of U.S. application Ser. No. 10/419,186, filed Apr. 21,2003, now U.S. Pat. No. 6,741,396; which is a continuation applicationof U.S. Ser. No. 10/166,089, filed Jun. 11, 2002, now U.S. Pat. No.6,567,218; which is a continuation of U.S. Ser. No. 09/734,164, filedDec. 12, 2000, now U.S. Pat. No. 6,411,440; which is a continuationapplication of U.S. Ser. No. 09/327,191, filed Jun. 7, 1999, now U.S.Pat. No. 6,201,645.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique of an apparatus fordisplaying images on a screen using a liquid crystal panel and an otherdisplay elements, for example, a liquid crystal projector, a reflectiontype image displaying projector, a liquid crystal television and aprojection type display apparatus.

A projection type imaging apparatus such as a liquid crystal projectorhas been popular, in which the display element such as a liquid crystalpanel or the like is irradiated with the light beam emitted from thelight source and thereby an image on the display element can beprojected as the enlarged image.

In the imaging apparatus of this type, the light from the light sourceis adjusted through conversion to gray scale of each pixel with thedisplay element and is then projected to the screen. For example, in thecase of the twisted nematic (TN) type liquid crystal display element inwhich the display element is a typical example of the liquid crystaldisplay element, two sheets of polarizing plates are arranged to resultin difference of 90 degrees of polarizing directions before and afterthe liquid crystal cell which is formed by supplying the liquid crystalto the space between a couple of transparent substrates having thetransparent electrode films. In this case, amount of transmitting lightof the incident light beam is controlled to display the image ofinformation by combining the operations for rotating the polarizingplane with the electro-optical effect of the liquid crystal andselecting the polarizing element of the polarizing plate. In recentyears, such transmitting type or reflection type display element hasremarkably reduced in size of the element itself and also has improvedperformance such as resolution, etc.

Therefore, with advancement in size reduction and performance of theapparatus utilizing the display element, a projection type imagingapparatus has newly been proposed as the apparatus not only forrealizing image formation by video signal or the like which has beendone in the related art and but also for use as an image output deviceof a personal computer. The projection type imaging apparatus of thistype is particularly required to be small in size and to assure thatbright image can be obtained up to the corners of the display screen.

However, the projection type imaging apparatus of the related art hasproblems that the apparatus size is large and brightness and quality ofimage attained finally are insufficient.

For example, in the case of liquid crystal display apparatus, sizereduction of the light bulb, namely liquid crystal element itself iseffective for size reduction of the apparatus as a whole, but when theliquid crystal display element is reduced in size, the area irradiatedby the light of liquid crystal means becomes small, raising a problemthat a ratio in amount of light flux on the liquid crystal displayelement for amount of total light flux radiated by the light source(hereinafter, referred to as light application efficiency) becomes lowerand side area of display screen becomes dark. Moreover, since the liquidcrystal display element can utilize the polarized light beam of only onedirection, about a half of the light beam emitted from the light sourcewhich radiates the random polarized light beam is left unused.

As a means for attaining the bright image at the four sides of thedisplay screen, an integrator optical system, for example, has beenproposed, in which a couple of lenses are used as described in theJapanese Published Unexamined Patent Publication No. HEI 3-111806. Theintegrator optical system divides the light from the light source with aplurality of condenser lenses in the shape of the rectangular openingforming a first array lens and then focuses in overlapping the outputlight in the shape of rectangular opening at the radiating surface(liquid crystal display element) with a second array lens formed by thecondenser leans group corresponding to the condenser lenses in the shapeof rectangular opening. In this optical system, intensity distributionof the light irradiating the liquid crystal display element can bealmost equalized. Meanwhile, as the optical system for irradiating theliquid crystal display element with the light beam emitted from thelight source and arranged in one polarizing direction, a system isdisclosed in the Japanese Published Unexamined Patent Publication No.HEI 4-63318, in which the light beam emitted from the light source andis polarized at random is isolated to the P-polarized light beam andS-polarized light beam using the polarizing beam splitter and these arethen combined with a prism.

However, in the conventional integrator optical system, since a diagonalsize of one lens cell of array lens is 0.25 inch or larger, an F valueof the light system must be set to almost 2 or 3 in order to improveequality of brightness and quality of image using the liquid crystaldisplay element with a micro-lens. As a result, distance between thefirst and second array lenses becomes not shorter than 31 mm, disablingreduction in size of the optical system. Therefore, it has beendifficult for the projection type liquid crystal apparatus of therelated art to reduce the size of apparatus exceeding the size of the A4file size. Moreover, even in the optical system utilizing the polarizingbeam splitter, it is difficult to realize matching in accuracy in thearray lens and therefore size reduction has also been difficult. As aresult, it has been difficult to simultaneously realize reduction insize of the apparatus as a whole and improvement in performance such asbrightness. In addition, in the case of the projection type liquidcrystal apparatus, it has also been difficult, even when only thelighting means is improved, to attain the display apparatus which issmall in size and assures good display image quality because the imagequality depends on various factors, in addition to such lighting means,such as optical characteristic of objection leans and opticalcharacteristic of liquid crystal element.

Moreover, it has been required to use a larger array lens in order toimprove brightness in the integrator optical system of the related artand when the projection type liquid crystal apparatus is reduced insize, brightness has been lowered. In addition, this phenomenon can alsobe observed when size reduction is conducted in the optical system usingthe polarizing beam splitter. As a result, it has been difficult tosimultaneously realize size reduction of the apparatus as a whole andimprovement in performance such as brightness. Moreover, when apolarized beam combining means is used, performance deterioration due tounwanted light beam, namely the P-polarized light beam entering the Slight path has also been observed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to improvedisadvantages of the related art explained above, assure sufficientbrightness and good image quality and provide the image displaytechnique which enables higher accuracy and sufficient reduction in sizeof apparatus.

In order to attain the objects explained above, the present inventionprovides the structure that:

-   (1) an array lens is provided, in which at least any one of the    diagonal size, vertical size and lateral size of lens cell is equal    to almost 1/(4.5 or more) for each corresponding size of a display    element which is irradiated by a lighting optical system;-   (2) an array leans is provided, in which a diagonal size of lens    cell is almost 0.18 inch or less;-   (3) an array lens is provided, in which the total number of lens    cells is almost 240 or more;-   (4) an array lens is provided, in which the lens focal distance of    lens cell is 30 mm or less;-   (5) a light shielding means is provided to eliminate unwanted light    beam to the light incident side than the light source unit or light    isolating means for isolating the light emitted from the array lens    to the P-polarized light beam and S-polarized light beam; and-   (6) a first array lens for condensing the light from the light    source unit to form a plurality of secondary light source image, a    second array lens for focusing a lens image of the first lens array    lens to the display element, an isolating means for isolating the    light beam emitted from the light source unit or from the array lens    into the P-polarized light beam and S-polarized light beam, and a    converting means for changing any one beam of the P-polarized light    beam and S-polarized light beam of the output light beam emitted    from the isolating means are arranged almost on the same optical    axis like the linear line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a preferred embodiment of the presentinvention.

FIG. 2 is a diagram illustrating a structure of the apparatus as apreferred embodiment of the present invention.

FIG. 3 is a diagram explaining the effect of a preferred embodiment ofthe present invention.

FIG. 4 is a diagram illustrating a preferred embodiment of the presentinvention.

FIG. 5 is a diagram illustrating the other preferred embodiment of thepresent invention.

FIG. 6 is a diagram illustrating the other preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be explainedwith reference to the accompanying drawings.

FIG. 1 illustrates a first preferred embodiment of the projection typeliquid crystal display apparatus of the present invention. In FIG. 1,the projection type liquid crystal display apparatus is provided with alight source 1. This light source 1 is formed of a super-high pressuremercury lamp, metal halide lamp, xenon lamp, mercury xenon lamp and awhite lamp such as halogen lamp. The light source 1 has at least onereflecting mirror 5 having a circular or polygonal light emittingaperture and an electrode wire 28 having the diameter, for example, of0.6 mm or less provided at one side of the lamp electrode in thereflecting mirror and the light beam emitted from this light source 1travels toward a projection lens 3 passing through a liquid crystaldisplay element 2 as a light bulb element and is then projected to ascreen 4.

The light beam radiated from a bulb of the light source 1 is condensedby a reflector 5 having the elliptical surface, parabolic surface ornon-spherical surface and then enters a first array lens 6. Afterpassing the first array lens 6, the light beam passes a second arraylens 7 and then enters a polarized beam splitter 8. This incident lightbeam is isolated, as the transmitting light beam, to the P-polarizedlight beam and S-polarized light beam by the polarized beam splitter 8,and the P-polarized light beam is rotated by 90 degrees in thepolarizing direction by a λ/2 phase difference plate 9 arranged at thelight emitting side surface of the polarized beam splitter 8 to becomethe S-polarized light beam and is then incident to a condenser lens 10.Moreover, the S-polarized light beam repeats reflection and is thenemitted from the light emitting surface of the neighboring polarizedbeam splitter 8 and then enters the condenser lens 10. The condenserlens 10 is formed of at least one or more sheet of lens having thepositive index of refraction and has a function to further condense theS-polarized light beam. The light beam having passed the condenser lens10 irradiates the liquid crystal display element 2. At the incident sideof this liquid crystal display element 2, an incident light polarizingplate 11 transmitting the S-polarized light beam is arranged.

In the projection type liquid crystal display apparatus of the relatedart, the polarized light beam of only one direction is transmittedthrough combination of the incident light polarizing plate 11, liquidcrystal display element 2 and light emitting side polarizing plate 12and thereby amount of light to be transmitted has been reduced to almosta half. However, since the polarized light beam splitter 8 is used inthe preferred embodiment, the polarizing directions of the randomlypolarized light beams emitted from the light source 1 are equalized inone polarizing direction and this light beam is then input to the liquidcrystal display element 2. Ideally, the brightness two times that of theprojection type liquid crystal display apparatus of the related art canbe attained.

Moreover, in this embodiment, the first array lens 6 and second arraylens 7 of the present invention are same in the type thereof and lateralsize of one lens cell has the ratio of almost 1/5.3 against the lateralsize of the liquid crystal display element. For example, when thediagonal size of rectangular image display means of the liquid crystaldisplay element 2 is 0.9 inch, the diagonal size of rectangular shape ofone lens cell is almost 0.17 inch, the total number of lens cellsforming the first array lens 6 and second array lens 7 is 240 or moreand the focal distance of one lens cell is 30 mm or less, therebyrealizing reduction in size of optical system. Moreover, individualimages of almost 240 or more cells are overlapped on the liquid crystaldisplay element 2 to obtain more uniform image quality than that of theapparatus of related art. In addition, since the cell size is 0.17 inch,even when the shadow of electrode wire 28 crosses the cell, imagequality may be equalized because the number of cells is 240 or larger(almost 16×15 cells). Accordingly, the projection type liquid crystaldisplay apparatus can realize simultaneously size reduction of theapparatus as a whole and improvement of brightness.

Furthermore, the present invention provides the effect that the unwantedlight beam is cut by the polarized beam splitter 8 formed by adding thelight shielding plate 11 to the optical axis incident surface of thereflection prism of the S-polarized light beam located at the center ofthe pitch of the optical axis of the first array lens 6 and/or secondarray lens 7, namely at the surface in the side of the first array lens6 and/or second array lens 7 and when unwanted light beam is absorbedand cut by the incident light polarizing plate 11, heat radiationoccurring when the light beam is converted to heat through energyconversion can be prevented. Moreover, color irregularity generated whenunwanted light beam enters the liquid crystal display element 2 can alsobe reduced.

Moreover, the polarized beam splitter 8 of the present invention 8 isformed thinner in the optical axis direction then the second array lens7 to realize shortening of the total length of optical system, lightweight of the optical unit and increase of F value of the lightingsystem. Thereby, since small size and light weight can be realized andmoreover F value of the projecting lens 3 can also be increased inconnection with the lighting system, the projecting lens 3 can also bereduced in size and weight.

The light beam having passed the liquid crystal display element 2reaches the display screen 4 passing the projecting means 3 such as, forexample, a zoom lens. An image formed on the liquid crystal displayelement 2 by the projecting means 3 is projected on the screen as theenlarged image by the function of the display apparatus.

Next, a practical embodiment of the present invention will be explained.

FIG. 2 is a schematic diagram illustrating the structure of theprojection type liquid crystal display apparatus of the presentinvention. The embodiment of FIG. 2 is a 3-plate type projection displayapparatus using three transmitting type liquid crystal display elements2 as the liquid crystal light bulbs corresponding to so-called threeprimary colors of R (Red), G (Green) and B (Blue). In this embodiment,the light beam emitted from the lamp 13 such as, for example, super-highpressure mercury lamp as the light source is once reflected by aparabolic reflection mirror type reflector 5 and is thereafter incidentto the first array lens 6 which is formed by a plurality of condenserlenses provided at the rectangular frame almost in the same size as thelight emitting aperture of such parabolic reflection mirror typereflector 5 to condense the light emitted from the lamp unit 14 and forma plurality of secondary light source images and then passes the secondarray lens 7 which is formed by a plurality of condenser lenses andlocated at the area near a plurality of secondary light source images tofocus individual lens images of the first array lens 5 to the liquidcrystal display element 2. This light beam emitted from the second arraylens 7 is incident to a line of rhombus prisms almost in the ½ size ofwidth of each lens arranged in such a manner as fitting to the pitch inthe lateral direction of the optical axis of lens of the second arraylens 7. A film of the polarized beam splitter 8 is formed on the surfaceof this prism and therefore the incident light beam is isolated to theP-polarized light beam and S-polarized light beam by the polarized beamsplitter 8. The P-polarized light beam travels in straight in thepolarized beam splitter 8, it is then rotated by 90 degrees in thepolarizing direction by the λ/2 phase difference plate 9 provided at thelight emitting surface of the prism and is then emitted after it isconverted to the S-polarized light beam. Meanwhile, the S-polarizedlight beam is reflected by the polarized beam splitter 8, it is thenreflected again in the intrinsic optical axis direction within theneighboring rhombus prism and it is emitted as the S-polarized lightbeam. Of course, the polarized beam splitter 8 of the present inventionadds a light shielding member 27 (see FIG. 4A and FIG. 4B) to theoptical axis incident surface of the reflection prism of the S-polarizedlight beam located at the center of the pitch of the optical axis ofeach lens of the second array lens 7, namely to the surface in the sideof the second array lens 7. Thereafter, light beam is condensed to theliquid crystal display element 2 by the condenser lens 10. In the courseof this process, the light beam emitted from the polarized beam splitter8 is bent in its optical path by 90 degrees with a total reflectionmirror 15 and a B (Blue), G (Green) reflection dichroic mirror 16 allowsthe R (Red) color light beam to pass and reflects the B, G lights. The Rlight beam having passed the dichroic mirror is bent in its optical pathby 90 degrees with the total reflection mirror 17 for R light beam,passes through the condenser lens 18 and incident polarizing plate 11provided before the liquid crystal display element, is incident to theliquid crystal display element 2 formed of an opposing electrode andliquid crystal or the like and then passes through the polarizing plate12 provided in the light emitting side of the liquid crystal displayelement 2.

The liquid crystal display element 2 is provided with the liquid crystaldisplay areas in such number (for example, 800 pixels in lateraldirection×600 pixels in vertical direction for each color of threecolors) corresponding to the display pixels. Depending on the signaldriven from the external side, polarizing angle of each pixel of theliquid crystal display element 2 changes and finally the light in thedirection matched with the polarizing direction of the polarizing plate12 is emitted and the light in the orthogonal direction is absorbed bythe polarizing plate 12. The light polarized by the intermediate angledetermines amount of light beam passing through the polarizing plate andamount of light beam absorbed by the polarizing plate in relation to thepolarizing angle of the polarizing plate 12. As explained above, animage is projected conforming to the external input signal.

The R light beam emitted from the polarizing plate 12 is reflected bythe dichroic prism 19 having the function to reflect the R light beam,then enters the projecting means 3 such as a zoom lens and is thenprojected to the display screen.

On the other hand, the B light beam and G light beam having passed theB, G transmitting dichroic prism 19 enter a G-reflection dichroic mirror20. This mirror 20 reflects the G light beam. The reflected G light beamthen passes through the condenser lens 18 and incident polarizing plate11 provided before the liquid crystal display element 2 and then entersthe liquid crystal display element 2 and passes through the polarizingplate 12 provided in the light emitting side of the liquid crystaldisplay element 2. The G light beam emitted from the polarizing plate 12passes through the dichroic prism 19 having the function to transmit theG light beam, enters the projection lens 3 and is then projected to thedisplay screen.

Meanwhile, the B light beam transmitted through the G reflectiondichroic mirror 20 passes through a relay lens 21, it is then bend inthe optical path by 90 degrees with a total reflection mirror 22 to passthrough the relay lens 21, thereafter it is then bent again in itsoptical path by 90 degrees with a total reflection mirror 23 to passthrough the condenser lens 18 and incident polarizing plate 11 providedbefore the liquid crystal display element, it enters the liquid crystaldisplay element 2 and finally passes through the polarizing plate 12provided in the light emitting side of the liquid crystal displayelement. The B light beam emitted from the polarizing plate 12 isreflected by the dichroic prism 19 having the function to reflect the Blight beam and thereafter enters the projection lens 3 for projection tothe display screen.

Moreover, the B light beam transmitted through the G reflection dichroicmirror 20 passes through the relay lens 21, it is then bent in itsoptical path by 90 degrees with the total reflection mirror 22 to passthe relay lens 21, thereafter it is bent again in its optical path by 90degrees with the total reflection mirror 23 to pass the condenser lens18 and incident polarizing plate 11 provided before the liquid crystaldisplay element, it enters the liquid crystal display element 11 to passthrough the polarizing plate 12 provided in the light emitting side ofthe liquid crystal display element 2. The B light beam emitted from thepolarizing plate 12 is reflected by the dichroic prism 19 having thefunction to reflect the B light beam and enters the projection lens 3for projection to the display screen.

As explained above, the light beams respectively corresponding to R, G,B are isolated and combined by the color isolating means and colorcombining means and the images of respective colors are combined on thescreen to attain the enlarged image by enlarging the image on the liquiddisplay element respectively corresponding to R, G, B with theprojection lens 3. In the same figure, the power supply circuit 24 andimage signal circuit 25 are arranged as illustrated in the figure andheat generated by the light source 1 is guided to the external side witha blowing fan 26. Moreover, in this embodiment, the light beams emittedrandomly from the light source are aligned in one direction andtherefore less amount of heat is generated from the incident polarizingplate.

Moreover, the light source and projecting means are arrange in such amanner that the optical axes thereof are orthogonal with each other andin addition, the apparatus as a whole can be reduced in size byarranging the power supply circuit 24 and image signal circuit 25 asillustrated in the figure via the color isolating and combining unitconsisting of the color isolating means and liquid crystal displayelement and color combining means.

In addition, in this embodiment, the first array lens 6 and the secondarray lens 7 used in the present invention are formed in the same shape,the lateral size of one lens cell has a ratio of about 1/5.3 of thelateral size of the liquid crystal display element 2. For instance, whenthe diagonal size of rectangular shape of the image display area of theliquid crystal display element 2 is 0.9 inch, the diagonal size ofrectangular shape of one lens cell of the fist array lens 6 and secondarray lens 7 is about 0.17 inch, the diagonal size of rectangular shapeof one lens cell of the first array lens 6 and second array lens 7 isabout 0.17 inch, the total number of lens cells forming the first arraylens 6 and second array lens 7 is about 240 or more and the focaldistance of one lens cell of the first array lens 6 and second arraylens 7 is 30 mm or less. As a result, size reduction of the opticalsystem can be attained. Moreover, individual images of almost 240 ormore cells are overlapped on the liquid crystal display element 2 andthereby more homogeneous image than that of the apparatus of related artcan be obtained.

In addition, even if the shadow of the electrode wire 28 is crossing thecell because the cell size is 0.17 inch, when the number of cellsexceeds about 240 cells (almost 15×15 cells), image quality can be moreequalized. Therefore, size reduction and improvement of brightness ofthe apparatus as a whole can be realized simultaneously in theprojection type liquid crystal display apparatus.

Moreover, when it is required to improve brightness and homogeneity ofimage using the liquid crystal display element with micro-lens or thelike, the F value of the lighting system must be set to about 2 to 3.Even in this case, an interval of the first array lens and second arraylens of the present invention can be reduced to the distance of 30 mm orless and as a result the size reduction of optical system can berealized.

Furthermore, in the present invention, since a polarizing and combiningmeans (in some cases, a light shielding member is added) is combined andthe polarized beam splitter 8 as the polarizing and combining means isformed thinner than the second array lens 7 (namely, the polarizing beamsplitter 8 is set to 2 mm or less when the second array lens 7 is about2.5±0.5 mm), length of optical path can be shortened and the totalreflection mirror 15 can be arranged closely, thereby resulting in sizereduction of the set.

In the embodiment of the present invention illustrated in FIG. 2, thelighting and optical system comprises a lamp unit 14, a first array lens6, a second array lens 7, a polarized beam splitter 8, a λ/2 phasedifference plate 9, a condenser lens 10 and a total reflection mirror 15and establishes the optical path until the part for isolating the lightbeam emitted from the lamp 13 to the R, G, B light beams. Moreover, theoptical unit includes the lighting and optical system to define theprocess up to the isolation of the light beam emitted from the lightingand optical system to the R, G, B light beams respectively using the B(Blue), G (Green) reflection dichroic mirror 16 and G reflectiondichroic mirror 20 or the like and also to define the optical path up tothe projecting means 3 via the dichroic prism 19 which allowsapplication of the isolated R, G, B light beams to the respective liquidcrystal display element 2, reflects the R light beam and B light beamand transmits the G light beam.

FIG. 3 is a diagram illustrating a part of effect of the firstembodiment of the present invention.

FIG. 3 illustrates the lighting and optical system of the projectiontype liquid crystal display apparatus. The light source 1 has a circularreflecting mirror 5 and an electrode wire 28 having the diameter ofalmost 0.6 mm or less provided at the single side of the lamp electrodewithin the reflecting mirror 5.

The light beam radiated from a bulb of the light source 1 is condensedby an elliptical surface or parabolic surface or non-spherical surfacereflector 5 and is then incident to the first array lens 6. Afterpassing the first array lens 6, the light beam passes the second arraylens 7 and then enters the polarized beam splitter 8. The transmittedlight of this incident light beam is isolated to the P-polarized lightbeam, while the reflected light thereof is isolated to the S-polarizedlight beam respectively by the polarized beam splitter 8. TheP-polarized light beam is rotated by 90 degrees in its polarizingdirection by the λ/2 phase difference plate 9 provided at the lightemitting side surface of the polarized beam splitter 8 to become theS-polarized light beam and enters the condenser lens 10. Moreover, theS-polarized light beam is repeatedly reflected and is then emitted fromthe light emitting surface of the neighboring polarized beam splitter 8to enter the condenser lens 10. The condenser lens 10 is formed of atleast a sheet of lens or more lenses having the positive index ofrefraction having the function to further condense the S-polarized lightbeam. The light beam having passed the condenser lens 10 irradiates theliquid crystal display element 2.

Referring to FIG. 3, the first array lens 6 and second array lens 7 ofthe present invention are formed in the same shape. The lateral size ofone lens cell has a ratio of almost 1/5.3 of the lateral size of theliquid crystal display element 2. For example, when the diagonal size ofrectangular shape of the image display area of the liquid crystaldisplay element 2 is 0.9 inch, the diagonal size of rectangular shape ofone lens cell of the first array lens 6 and second array lens 7 isalmost equal to the size of 0.17 inch, the total number of lens cellsforming the first array lens 6 and second array lens 7 is 240 or moreand the lens focal length of one lens cell of the first array lens 6 andsecond lens array 7 (FIG. 3 is a schematic diagram) is 30 mm or less.Accordingly, size reduction of optical system can be attained. Moreover,as indicated by dotted line of FIG. 3, individual images of 240 cells ormore are overlapped on the liquid crystal display element 2 and morehomogeneous image quality than that of the related art can be obtained.In addition, since the cell size is 0.17 inch, even if the shadow of theelectrode wire 28 crosses the cell, when the number of cells is about240 (almost 16×15 cells) or more, seven (7) to eight (8) lines arearranged in the single side. When the cell size is 0.17 inch, six linesof belt type shadow having the width of almost 0.6 mm are arranged inone cell size. Therefore, when at least six lines are arranged in thesingle side of cell, dark area resulting from shadow of the electrodewire 28 on the liquid crystal display element can be freed and resultantcolor irregularity can also be eliminated and homogeneous image qualitycan be attained. In this case, since the electrode wire exists in thesingle side of the right and left sides of the optical axis center, whenone to two lines are provided as the allowance of the vertical orhorizontal arrangement of array lens, 14 to 16 lines in minimum arerequired. Accordingly, when the number of cells is about 240 or more,shadow of the electrode wire of almost 0.6 mm or less is reflectedequally like the diagonal line of the figure on the liquid crystaldisplay element. Thereby, image quality assuring equal brightness and nocolor irregularity can be attained.

Therefore, the projection type liquid crystal display apparatus cansimultaneously realize reduction in size and improvement in brightnessof the apparatus as a whole. Moreover, since the first array lens 6 andsecond array lens 7 are formed in the same shape, only one type is usedand cost reduction can also be attained.

FIG. 4 is a diagram illustrating the second embodiment of the presentinvention.

The polarized beam splitter 8 illustrated in FIG. 4A and FIG. 4B isprovided with a polarized beam splitter film at the glass plate thereoffor isolating the P-polarized light beam and S-polarized light beam.After this film is laminated using a bonding agent, the glass plate issliced in the angle of 45 degrees. Therefore, as illustrated in FIG. 4,there is provided a flat plate structure wherein a plurality oflongitudinally elongated rhombus prisms are arranged. Such filming maybe attained by conducting the mirror evaporation of aluminum or silveror the like in every other surface. However, since this mirror sectionhas a role of reflecting the S-polarized light beam, it is required toprovide a certain means for not allowing the light beam to enter thelight path of the prism.

Therefore, the polarized beam splitter 8 of the present invention adds alight shielding member 27 to the optical axis incident surface of theS-polarized light beam reflection prism located at the center of thepitch of the optical axis of each lens of the second array leans 7,namely to the surface in the side of the second array lens 7 to providethe effect that unwanted light beams can be cut and when the light beamis absorbed and cut by the incident polarizing plate 11, the heatgenerated through energy conversion from the light beam to heat energycan be prevented. This light shielding member 27 is formed of slit typereflection films, or ground glass type dispersion films, or metal sealfor light shieldings, or heat-proof seals, or slitted metal plates, ormetal plating, or the like in every other one formed with silver oraluminum evaporation film.

In the flat plate structure where a plurality of polarized beamsplitters 8 are arranged as explained above, they are bonded in everyother line, it is also possible that the isolated P-polarized light beamis converted to the S-polarized light beam, the light beam emitted fromthe polarized beam splitter 8 is totally set to the S-polarized lightbeam, or after the isolated S-polarized light beam is emitted byreflection from the prism adjacent to the incident prism, the light beamemitted from the polarized beam splitter 8 is totally set to theP-polarized light beam with the λ/2 phase difference plates 9.

When a plurality of rhombus prisms of the flat type polarized beamsplitter 8 explained above are arranged conforming to the pitch, in thelateral arrangement direction, of the lens optical axis of the secondarray lens 7 and one polarized beam splitter 8 and the other polarizedbeam splitter 8 are bonded symmetrically in the right and left sides ofthe center under the condition rotated each other by 180 degrees in sucha manner that the second array lens 7 is divided respectively to halfareas in the right and left or upper and lower sections keeping aclearance, for example, h equal to ½ of the width of the optical axispitch at the center of the second array lens 7, the light shieldingmember 27 provided in the second array lens 7 can be matched in higheraccuracy with the pitch in the lateral arrangement direction of thepolarized beam splitter 8 and thereby highly accurate bonding among thesecond array lens 7, light shielding member 27 and polarized beamsplitter 8 which has been considered difficult in manufacturing processcan be realized.

In the structure of the related art, since the light transmittingefficiency is lowered even when interface is formed of reflection-prooffilm in such a case that the flat type polarized beam splitter 8 formedsymmetrically in the right and left direction as illustrated in FIG. 4Aor FIG. 4B and interface between optical parts such as this polarizedbeam splitter 8 and second array lens 7 is formed of the layer of air,this polarized beam splitter 8 and the second array lens 7 are bondedconforming to the pitch in the lateral arrangement direction of the lensoptical axis and the polarized beam splitter 8. In this case, the slittype light shielding plate to cut the unwanted light beam is arrangedbefore the second array lens 7, namely in the side of light source inview of shielding the unwanted light element, namely the hatched elementin the FIG. 4B before the light beam enters the polarized beam splitter8. However, in this case, the light shielding member 27 is formed of amember such as metal plate having a slit and therefore it must besupported independent of the optical axis.

For this reason, the required light beam also has been shielded due topart accuracy error or assembling accuracy error of the light shieldingmember 27 and the number of parts has also been increased even in thecase of assembling, resulting in increase of processing cost.

However, in the present invention, since the polarized beam splitter 8is bonded symmetrically in the right and left direction in both sides ofthe center to the second array lens 7 providing the light shieldingmember 27 and the light shielding member 27 is formed of an evaporationfilm or the like, the light incident surface of the prism in the S lightpath can be shielded almost without any error and the number of partscan also be reduced to improve the assembling efficiency.

Moreover, in the present invention, the process of the second stage thatthe flat type polarized beam splitter 8 which is symmetrical in theright and left direction is produced by a maker and is then bonded tothe second array lens 7 like the prior art is eliminated but a couple ofpolarized beam splitters 8 are bonded to the second array lens 7 in theprocess of the first stage. As a result, processing cost can be lowered.

In addition, since the polarized beam splitter 8 of the related art isintegrated in the right and left sides, the bonding accuracy isoverlapped from the left end to the right end and therefore when thebeam splitter 8 is bonded to the second array lens 7, it is shared atthe center to the right and left side, certainly resulting in thebonding accuracy error in the right and left sides, for example, theerror of ±0.25 in both right and left sides.

However, in the present invention, since the polarized beam splitter 8is bonded to the second array lens 7 providing individual lightshielding members 27 in the right and left sides, the accuracy errorfrom the center is never accumulated and therefore since the leftpolarized beam splitter 8 can define the left center thereof or the lensoptical axis of the left half on the second array lens 7 in a largeamount of light beam as the center for accuracy sharing, the accuracyerror can be controlled to ±0.125 in the numerical value. When the rightside polarized beam splitter 8 is bonded to the second array lens 7 inthe same manner, the effect to reduce the bonding accuracy error canalso be attained as in the case of the left side. Thereby, positionaldisplacement of the optical axis due to the bonding error of thepolarized beam splitter 8 in the half width of the lens optical axispitch of the second array lens 7 can be reduced and amount of incidentlight beam from the second array lens 7 to be reflected by the polarizedbeam splitter 8 can also be reduced. Accordingly, the light transmittingefficiency can be improved to realize improvement in brightness. Thepolarized beam splitter 8 is naturally formed thinner than the first orsecond array lens 7 and when it is required to shield the light beamwith an evaporation film, the evaporation system is different from thatwhen the polarized beam splitter 8 formed thicker than the ordinarysecond array lens 7 is used. Namely, it is necessary for not cutting thelight beam to be used to set the area of the light shielding means torealize light shielding for rather narrower area by considering thebonding accuracy error rather than the P-polarized light beam apertureor S-polarized light beam aperture of the polarized beam splitter 8 forlight shielding.

Such accuracy of light shielding means, for example, an idea for makingthe width of light shielding film a little smaller than the pitch widthof the polarized beam splitter 8 is effective for improvement of lightefficiency when a larger number of cells are used for the polarized beamsplitter 8 which is thinner than the second lens array 7 and the secondlens array 7. Moreover, in some cases, it is also effective that manyreference positions are prepared and the polarized beam splitter 8 isdivided for the bonding as will be explained later considering thebonding accuracy.

FIG. 5 is a diagram illustrating the external view of the thirdembodiment of the present invention. In the present invention, the firstarray lens 6 or second lens array 7 is provided with a first positioningsection 27 as the positioning reference of each lens and the polarizedbeam splitter 8 is also provided a second positioning section 28 as thepositioning reference. This first positioning section 27 and the secondpositioning section 28 are respectively formed by the engraving(illustrated in FIG. 5), recessed area, projected area, end surface,cutout area, stepped area or marking or the like and the absolutepositioning of the first array lens 6 or second array lens 7 can beperformed by aligning the first positioning section 27 to thepositioning area (not illustrated) provided to the structure member forsupporting and fixing the first array lens 6 or second array lens 7. Inthe same manner, the absolute positioning of the polarized beam splitter8 can also be performed by aligning the second positioning section 28 ofthe polarized beam splitter 8 to the positioning area (not illustrated)provided to the structure member for supporting and fixing the polarizedbeam splitter 8.

According to the present invention, respective reference positioning canbe made easily when assembling the first array lens 6, second array lens7 and polarized beam splitter 8 to the optical part supporting structuremember and relative lens optical axes of the first array lens 6 andarray lens 7 may be matched at the design position and arrangement ofpolarized beam splitter 8 can be located at the position resulting inthe maximum light application efficiency conforming to the lateralarrangement pitch of the lens optical axis explained above. Thereby,optical performance can be improved and the assembling work of theseoptical parts can be simplified to improve the working efficiency.

In addition, as illustrated in FIG. 5, the polarized beam splitter 8 canbe arranged to the optimum position for each lens optical axis of thesecond array lens 7 by providing the first positioning section 27 of thesecond array lens 7 and the second positioning section 28 of thepolarized beam splitter 8 to the positions to be matched and thenmatching these positioning sections at the time of assembling. Thereby,matching can be made to the position providing the maximum lightapplication efficiency in view of improving the optical performance.

FIG. 6 is a diagram illustrating the external appearance of the fourthembodiment of the present invention. In the present invention, the firstarray lens 6 or second array lens 7 is provided with the firstpositioning section 27 as the positioning reference of each leans andthe polarized beam splitter 8 is provided with the second positioningsection 28 as the positioning reference. These first positioning section27 and second positioning section 28 are formed as the recessed area andprojected area as illustrated in FIG. 6A. These first and secondpositioning sections 27, 28 are combined to match the projected area andrecessed area for the positioning so that the polarized beam splitter 8is located at the optimum position for the lens optical axis of eachlens of the first array lens 6 or second array lens 7 and thereafter thepolarized beam splitter 8 can be bonded to the first array lens 6 or thesecond array lens 7. Accordingly, matching can be made to the positionproviding the maximum application efficiency of the light and bondingexplained above assures reduction in amount of light reflected at theinterface of the optical elements and improvement in the opticalperformance.

In addition, the first positioning section 27 and second positioningsection 28 are not limited to the recessed area and projected area andthese may be FIG. 6B in which end faces of each part are positioned soas to coincidence with optical axes as illustrated, or FIG. 6C the firstpositioning section 27 is positioned in the second positioning section28 as illustrated, or FIG. 6D the type where entire part of onepositioning frame is engaged with the other frame as illustrated, orFIG. 6E the type where both sections are positioned and bonded via athird member such as the positioning jig 31 or the like as illustrated.Moreover, it is also possible to improve accuracy by designing thesizes, considering the accumulated element accuracy error, so that thepolarized beam splitter 8 is located to the optimum position for eachlens optical axis of the array lens.

According to the present invention, length of optical path can beshortened and the apparatus can be reduced in size. Brightness can alsobe improved. Moreover, image quality improvement such as equalization ofimage quality can also be realized. In addition, generation of heat dueto unwanted light beam can also be prevented.

The present invention allows any modification of the embodimentexplained above without departing from the spirit and scope of theprincipal characteristics thereof. The embodiment explained above istherefore only an example of the present invention and should not belimited thereto. The scope of the present invention is limited only bythe appended claims. Moreover, any modifications and changes in regardto the appended claims should be within the scope of the presentinvention.

1. An image display apparatus, comprising: a light source unit having atleast part of a reflection mirror; a first array lens, being constructedwith plural numbers of condenser lenses, for forming plural numbers ofsecondary light source images through condensing a light emitted fromsaid light source unit; a second array lens, being constructed withplural numbers of condenser lenses, and being disposed in vicinity wheresaid secondary light source images are formed; a lighting optic systemhaving a function of irradiating the light emitted from said lightsource unit upon a surface to be irradiated; an image display elementfor modulating the light; a polarized light beam splitting unit, havinga first polarized light beam splitter and a second polarized light beamsplitter, corresponding to respective half areas when said second arraylens is equally divided horizontally or vertically, while providing agap at a central portion therebetween, and also light shielding members,being provided on surfaces of said first and second polarized light beamsplitters, opposing said second array lens, and being provided in lightreflecting portions thereof, wherein said second polarized light beamsplitter is so disposed that said first polarized light beam splitter isrotated by 180° around an optical axis thereof; and a projection lensfor projecting the light emitted from said image display element.
 2. Theimage display apparatus, according to claim 1, wherein each of saidfirst and second polarized light beam splitters comprises a polarizedlight beam splitter, for dividing the light into a P-polarized lightbeam, and a S-polarized light beam, a λ/2 phase difference plate, forrotating the light emitted from said polarized light beam splitter,either the P-polarized light beam or the S-polarized light beam, inpolarization direction thereof, and a reflection surface, for reflectingthe polarized light, either said P-polarized light beam or saidS-polarized light beam thereupon, being provided for each of lines oflenses of said second array lens.
 3. The image display apparatus,according to claim 1, wherein said gap provided at the central portionof said second array lens has a width being nearly equal to a half (½)of a pitch between respective lenses of said second array lens, in avertical or horizontal direction of arrangement thereof.
 4. The imagedisplay apparatus, according to claim 1, wherein said polarized lightsynthesizing unit has a thickness being equal to or less than that of atleast one of said first array lens and said second array lens, in adirection of an optical axis thereof.
 5. The image display apparatus,according to claim 1, wherein said polarized light beam splitting unitis adhered on said second array lens.
 6. The image display apparatus,according to claim 1, wherein the light shielding member of saidpolarized light beam splitting unit is made of an evaporated film forexclusive use of reflection.
 7. The image display apparatus, accordingto claim 1, wherein the light shielding member of said polarized lightbeam splitting unit is made of a metal plate for exclusive use ofreflection.
 8. The image display apparatus, according to claim 1,wherein said light shielding member of said polarized light beamsplitting unit comprises a dispersion surface of ground glass type.